This invention relates to operation of a plurality (consist) of locomotives used to pull a train of cars; and, more particularly, to configuring the locomotives prior to entering a confined area such as a tunnel, snow shed, or other environmental restrictive area which may deprive a locomotive of combustible air and effect cooling of a locomotive's engine. It further relates to operation of the locomotives during passage through the tunnel, shed or area, and recovery of the engine upon exiting the tunnel, shed or area.
Referring to FIGS. 1A and 1B, a train T is shown to include a number of engines or locomotives L1-Ln for pulling a train of cars C. The number of locomotives required is a function of the weight of the cars comprising the train and the tonnage of the lading they carry. In FIG. 1A, the locomotives are shown connected together at the head of the train. In FIG. 1B, the locomotives are shown positioned at intervals along the length of the train. These are the two most common configurations. Regardless of the arrangement of locomotives, it is important that the combined tractive effort from all the locomotives be sufficient to move the train over a desired route despite the conditions encountered during transit.
One condition periodically effecting train operation is its passage through a confined area such as a tunnel. Tunnels vary in length from relatively short to more than two miles in length. On some routes tunnels are few and far apart. On other routes, there are many tunnels and they are spaced quite close together. Tunnels create two problems significantly effecting locomotive performance. First, because of the confined space within a tunnel, the amount of air available for combustion in a locomotive's diesel engine can be severely limited. Second, air does not necessarily circulate very well within a tunnel. The resulting reduced air-flow effects the degree to which a locomotive's engine can be cooled. Overheating can ruin an engine. As a rule, when a diesel engine's oil temperature reaches approximately 230° F., it is necessary to begin reducing the engine's output power. This is commonly referred to as “derating” the engine. If the oil temperature reaches approximately 240° F., then it is important to effectively take the engine off-line and place it in an “idle” mode of operation.
During passage through a tunnel, and referring to FIGS. 1A and 1B, lead locomotive L1 will have more air available to it than locomotive L2; locomotive L2 more air than the next locomotive, and so forth. As the lead engines pass through the tunnel, their exhaust gases fill up the tunnel space, depleting the amount of air available to the remaining locomotives for combustion. In addition, the temperature in the tunnel rises as a result of the heat produced by the exhaust gases from the diesel engines. As tunnel temperature increases, there will be less heat dissipation from the trailing locomotives, because the temperature differential between the engine and the atmosphere has decreased. As a result, and the temperatures of these locomotives will tend to rise faster than the corresponding engine temperatures of the lead locomotives.
Those skilled in the art will appreciate that the above described problems mostly effect freight trains which travel through tunnels at fairly low rates of speed (8–10 mph) as opposed to passenger trains which typically have fewer cars, less weight, and travel through tunnels at higher speeds. However, passenger trains are subject to the same problems.
Currently, in multi-locomotive train operations, each locomotive is separately derated prior to entering a tunnel, the tractive effort of each locomotive being based upon factors including the cooling system capabilities of the locomotive, the altitude at which the train is operating, and ambient air temperature, among others. Altitude is important because the higher the elevation of the tunnel, the less oxygen there is. Ambient temperature is important because the cooler the temperature the greater the amount of heat which can be transferred from the engine to the atmosphere to cool the engine.
Because current tunnel operations involve a separate configuration of each engine for passage through the tunnel, and because changes to a locomotive may be necessary after entering the tunnel, due to oxygen availability, air circulation, and heat loads in the tunnel, operation of the train is inefficient, also, breakdowns can occur. There is nothing presently available to optimize locomotive configuration prior to tunnel entry, and subsequently to control configuration changes in response to tunnel conditions. There is also not a procedure currently available to optimize engine recovery as the locomotives approach the tunnel exit and leave the tunnel.